Recently, molded motors to be mounted in electrical apparatuses such as a ventilator have been required to be small, thin and light with high quality maintained. Conventionally, as molded motors of this type, a configuration disclosed in Patent Document 1 has been known.
Hereinafter, the molded motor is described with reference to FIG. 4. FIG. 4 shows a structure of a printed circuit board to be mounted in a conventional molded motor.
As shown in FIG. 4, printed circuit board 111 is provided with oblong slits 114 between through holes 112 for lead wires. In molding, by pouring molded resin between slits 114, a molded motor in which insulation between through holes 112 is secured and a creepage distance therebetween is secured is achieved.
According to such a conventional molded motor, since the resin poured into oblong slit 114 flows in the longitudinal direction of slit 114, glass fibers contained in the resin are oriented along the direction. Therefore, when a mold shrinkage rate of resin is large or when the content of a mold release agent made of a metallic soap contained in the resin is large, the amount of glass fibers aligned in the board thickness direction of the printed circuit board is small due to stress concentration and tensile strength between the resin and the printed circuit board. As a result, peeling in an interface between the resin and the printed circuit board occurs.
Herein, the stress concentration occurs due to mold shrinkage at the time when resin is molded and solidified or due to the difference in the coefficient of linear expansion between the printed circuit board and the resin. Furthermore, the tensile strength between the resin and the printed circuit board occurs due to tension of the resin to a mold at the time when the resin is demolded from the mold.
When a molded motor is used in high-temperature and high-humidity space, tracking between through holes 112 may occur. Therefore, high-quality molded motors, in which resin is resistant to stress concentration due to mold shrinkage and the like and to tensile strength at the time of demolding and peeling in an interface between resin and a printed circuit board does not occur, are demanded.